Is 4x^2+y^2+16x-6y+9=0 a parabola, a circle, an ellipse, or a hyperbola?

1 Answer
May 11, 2018

An ellipse with vertical major axis.

Explanation:

4x^2+y^2+16x-6y+9=0

Convert to standard form by completing the square:

4x^2+16x+y^2-6y=-9

4(x^2+4x+4)+(y^2-6y+9)=-9+16+9

4(x+2)^2+(y-3)^2=16

(x+2)^2/4+(y-3)^2/16=1

Equation of an ellipse with vertical major axis in standard form:
(x-h)^2/a^2+(y-k)^2/b^2=1
Where:
(h, k) is the coordinate of the center
2b is the major axis

So in this case:
Center is at (-2, 3)
a=2, b=4
Major axis is along the y-axis and the length is: 8